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A QUIC implementation in Java
/*
* Copyright © 2020, 2021, 2022, 2023 Peter Doornbosch
*
* This file is part of Kwik, an implementation of the QUIC protocol in Java.
*
* Kwik is free software: you can redistribute it and/or modify it under
* the terms of the GNU Lesser General Public License as published by the
* Free Software Foundation, either version 3 of the License, or (at your option)
* any later version.
*
* Kwik is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
* more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see EMPTY_CALLBACK = f -> {};
protected final VersionHolder quicVersion;
protected final EncryptionLevel level;
protected final SendRequestQueue requestQueue;
protected final AckGenerator ackGenerator;
private final PacketNumberGenerator packetNumberGenerator;
protected long nextPacketNumber;
private volatile boolean stopping;
private Consumer finalizerCallback;
public PacketAssembler(VersionHolder version, EncryptionLevel level, SendRequestQueue requestQueue, AckGenerator ackGenerator) {
this(version, level, requestQueue, ackGenerator, new PacketNumberGenerator());
}
public PacketAssembler(VersionHolder version, EncryptionLevel level, SendRequestQueue requestQueue, AckGenerator ackGenerator, PacketNumberGenerator pnGenerator) {
quicVersion = version;
this.level = level;
this.requestQueue = requestQueue;
this.ackGenerator = ackGenerator;
packetNumberGenerator = pnGenerator;
}
/**
* Assembles a QUIC packet for the encryption level handled by this instance.
* @param remainingCwndSize
* @param availablePacketSize
* @param sourceConnectionId can be null when encryption level is 1-rtt; but not for the other levels; can be empty array though
* @param destinationConnectionId
* @return
*/
Optional assemble(int remainingCwndSize, int availablePacketSize, byte[] sourceConnectionId, byte[] destinationConnectionId) {
final int available = Integer.min(remainingCwndSize, availablePacketSize);
QuicPacket packet = createPacket(sourceConnectionId, destinationConnectionId);
List> callbacks = new ArrayList<>();
AckFrame ackFrame = null;
// Check for an explicit ack, i.e. an ack on ack-eliciting packet that cannot be delayed (any longer)
if (requestQueue.mustAndWillSendAck()) {
if (ackGenerator.hasNewAckToSend()) {
ackFrame = ackGenerator.generateAck().get(); // Explicit ack cannot disappear by other means than sending it.
// https://tools.ietf.org/html/draft-ietf-quic-transport-29#section-13.2
// "... packets containing only ACK frames are not congestion controlled ..."
// So: only check if it fits within available packet space
if (packet.estimateLength(ackFrame.getFrameLength()) <= availablePacketSize) {
packet.addFrame(ackFrame);
callbacks.add(EMPTY_CALLBACK);
ackGenerator.registerAckSendWithPacket(ackFrame, packet.getPacketNumber());
}
else {
// If not even a mandatory ack can be added, don't bother about other frames: theoretically there might be frames
// that can be fit, but this is very unlikely to happen (because limit packet size is caused by coalescing packets
// in one datagram, which will only happen during handshake, when acks are still small) and even then: there
// will be a next packet in due time.
// However, the ack removed from the queue must be returned
requestQueue.addAckRequest();
return Optional.empty();
}
}
}
int optionalAckSize = 0;
if (ackFrame == null && requestQueue.hasRequests()) {
// If there is no explicit ack, but there is something to send, ack should be included if possible
if (ackGenerator.hasAckToSend()) {
ackFrame = ackGenerator.generateAck().orElse(null);
if (ackFrame != null) {
optionalAckSize = ackFrame.getFrameLength();
}
}
}
if (requestQueue.hasProbeWithData()) {
List probeData = requestQueue.getProbe();
// Probe is not limited by congestion control, but it is limited by max packet size.
int estimatedSize = packet.estimateLength(probeData.stream().mapToInt(f -> f.getFrameLength()).sum());
if (estimatedSize > availablePacketSize) {
QuicFrame probeFrame = new PingFrame();
if (packet.estimateLength(probeFrame.getFrameLength()) > availablePacketSize) {
return Optional.empty();
}
probeData = List.of(probeFrame);
}
packet.setIsProbe(true);
packet.addFrames(probeData);
return Optional.of(new SendItem(packet));
}
if (requestQueue.hasRequests()) {
// Must create packet here, to have an initial estimate of packet header overhead
int estimatedSize = packet.estimateLength(1000) - 1000; // Estimate length if large frame would have been added; this will give upper limit of packet overhead.
while (estimatedSize < available) {
// First try to find a frame that will leave space for optional frame (if any)
int proposedSize = available - estimatedSize - optionalAckSize;
Optional next = requestQueue.next(proposedSize);
if (next.isEmpty() && optionalAckSize > 0) {
// The optional ack does not fit, try without
proposedSize = available - estimatedSize;
next = requestQueue.next(proposedSize);
}
if (next.isEmpty()) {
// Nothing fits within available space
break;
}
QuicFrame nextFrame = next.get().getFrameSupplier().apply(proposedSize);
if (nextFrame != null) {
if (nextFrame.getFrameLength() > proposedSize) {
throw new RuntimeException("supplier does not produce frame of right (max) size: " + nextFrame.getFrameLength() + " > " + (proposedSize) + " frame: " + nextFrame);
}
estimatedSize += nextFrame.getFrameLength();
packet.addFrame(nextFrame);
callbacks.add(next.get().getLostCallback());
// If there was an optional ack (which was not added yet)...
if (optionalAckSize > 0 && estimatedSize + optionalAckSize <= available) {
// ..., add it now (now that it is certain there will be at least one non-ack frame)
packet.addFrame(ackFrame);
callbacks.add(EMPTY_CALLBACK);
ackGenerator.registerAckSendWithPacket(ackFrame, packet.getPacketNumber());
estimatedSize += ackFrame.getFrameLength();
// Adding once will do ;-)
optionalAckSize = 0;
}
}
}
}
if (requestQueue.hasProbe() && packet.getFrames().isEmpty()) {
requestQueue.getProbe();
packet.setIsProbe(true);
packet.addFrame(new PingFrame());
callbacks.add(EMPTY_CALLBACK);
}
Optional assembledItem;
if (packet.getFrames().isEmpty()) {
// Nothing could be added, discard packet and mark packet number as not used
restorePacketNumber();
assembledItem = Optional.empty();
}
else {
assembledItem = Optional.of(new SendItem(packet, createPacketLostCallback(packet, callbacks)));
}
if (stopping && requestQueue.isEmpty(false)) {
if (finalizerCallback != null) {
finalizerCallback.accept(this);
}
}
return assembledItem;
}
protected long nextPacketNumber() {
return packetNumberGenerator.nextPacketNumber();
}
protected void restorePacketNumber() {
packetNumberGenerator.restorePacketNumber();
}
private Consumer createPacketLostCallback(QuicPacket packet, List> callbacks) {
if (packet.getFrames().size() != callbacks.size()) {
throw new IllegalStateException();
}
return lostPacket -> {
for (int i = 0; i < callbacks.size(); i++) {
if (callbacks.get(i) != EMPTY_CALLBACK) {
QuicFrame lostFrame = lostPacket.getFrames().get(i);
callbacks.get(i).accept(lostFrame);
}
}
};
}
protected QuicPacket createPacket(byte[] sourceConnectionId, byte[] destinationConnectionId) {
QuicPacket packet;
switch (level) {
case Handshake:
packet = new HandshakePacket(quicVersion.getVersion(), sourceConnectionId, destinationConnectionId, null);
break;
case App:
packet = new ShortHeaderPacket(quicVersion.getVersion(), destinationConnectionId, null);
break;
case ZeroRTT:
packet = new ZeroRttPacket(quicVersion.getVersion(), sourceConnectionId, destinationConnectionId, (QuicFrame) null);
break;
default:
throw new RuntimeException(); // programming error
}
packet.setPacketNumber(nextPacketNumber());
return packet;
}
public void stop(Consumer finalizer) {
this.finalizerCallback = finalizer;
requestQueue.clear(false);
stopping = true;
}
@Override
public String toString() {
return "PacketAssembler[" + level + "]";
}
}